Share

Trending Discussions

New Breakthrough Will Change How Oil Reserves Are Measured

A Massachusetts Institute of Technology team of researchers has taken the first three-dimensional images of kerogen’s internal structure, with a level of detail more than 50 times greater than has been previously achieved. The images should allow more accurate predictions of how much oil or gas can be recovered from any given formation.

The fossil fuels that provide much of the world’s energy originate in a type of rock known as kerogen, and the potential for recovering these fuels depends crucially on the size and connectedness of the rocks’ internal pore spaces.

(Click to enlarge)

Using a high-resolution system called electron tomography, researchers probed a tiny sample of kerogen to determine its internal structure. At left, the sample as seen from the outside, and at right, the detailed 3-D image of its internal pore structure. Image Credit: MIT. Click image for the largest view.

These new images should allow more accurate predictions of how much oil or gas can be recovered from any given formation. But this wouldn’t change the capability for recovering these fuels, but it could, for example, lead to better estimates of the recoverable reserves of natural gas, which is seen as an important transition fuel as the world tries to curb the use of coal and oil.

The team, which published results two years ago on an investigation of kerogen pore structure based on computer simulations, used a relatively new method called electron tomography to produce the new 3-D images, which have a resolution of less than 1 nanometer, or billionth of a meter. Previous attempts to study kerogen structure had never imaged the material below 50 nanometers resolution, Pellenq said.

Fossil fuels, as their name suggests, form when organic matter such as dead plants gets buried and mixed with fine-grained silt. As these materials get buried deeper, over millions of years the mix gets cooked into a mineral matrix interspersed with a mix of carbon-based molecules. Over time, with more heat and pressure, the nature of that complex structure changes.

The process, a slow pyrolysis, involves “cooking oxygen and hydrogen, and at the end, you get a piece of charcoal,” Pellenq explains. “But in between, you get this whole gradation of molecules,” many of them useful fuels, lubricants, and chemical feedstocks.

The new results show for the first time a dramatic difference in the nanostructure of kerogen depending on its age. Relatively immature kerogen (whose actual age depends of the combination of temperatures and pressures it has been subjected to) tends to have much larger pores but almost no connections among those pores, making it much harder to extract the fuel. Mature kerogen, by contrast, tends to have much tinier pores, but these are well-connected in a network that allow the gas or oil to flow easily, making much more of it recoverable, Pellenq explained.

The study also reveals that the typical pore sizes in these formations are so small that normal hydrodynamic equations used to calculate the way fluids move through porous materials won’t work. At this scale the material is in such close contact with the pore walls that interactions with the wall dominate its behavior. The research team thus had to develop new ways of calculating the flow behavior.

“There’s no fluid dynamics equation that works in these subnanoscale pores,” he said. “No continuum physics works at that scale.”

To get these detailed images of the structure, the team used electron tomography, in which a small sample of the material is rotated within the microscope as a beam of electrons probes the structure to provide cross-sections at one angle after another. These are then combined to produce a full 3-D reconstruction of the pore structure. While scientists had been using the technique for a few years, they hadn’t applied it to kerogen structures until now. The imaging was carried out at the CINaM lab of CNRS and AMU, in France (in the group of Daniel Ferry), as part of a long-term collaboration with MultiScale Materials Science for Energy and Environment, the MIT/CNRS/AMU joint lab located at MIT.

“With this new nanoscale tomography, we can see where the hydrocarbon molecules are actually sitting inside the rock,” Pellenq said. Once they obtained the images, the researchers were able to use them together with molecular models of the structure, to improve the fidelity of their simulations and calculations of flow rates and mechanical properties. This could shed light on how production rates decline in oil and gas wells, and perhaps on how to slow that decline.

So far, the team has studied samples from three different kerogen locations and found a strong correlation between the maturity of the formation and its pore size distribution and pore void connectivity. The researchers now hope to expand the study to many more sites and to derive a robust formula for predicting pore structure based on a given site’s maturity.

This is highly interesting work. Of all the oil and gas discovered so far less than half has been recovered and marketed. Those reservoirs are found, infrastructure installed and connected to markets. Secondary and tertiary recovery are already very big businesses indeed.

So one has to wonder if the big private petroleum firms may or may not be at this point or beyond. These firms hire the best petroleum engineers in the world and petroleum engineers are all very bright folks indeed.

But the research is offering, out in the open, real basic information and importantly, perspective.

Only half of all oil deposits discovered have been recovered. The oil is there and the holes are drilled. Supply is assured for decades. The price of oil is coming down to average recovery costs.

Gary Jakacky on December 03 2018 said:

Keragen is not a rock. The rock is various types of shale. Keragen is the waxy/oily petrochemical which they hope to harvest from the rocks.

Very informative article though, and i like that it makes clear that the transitional products between keragen and the "oil" are valuable also.

People who say "fossil fuels are doomed because of alternative energy" forget the countless uses these products have as plastics and similar items.

David Messler on December 03 2018 said:

This article is a little confusing as it ascribes reservoir properties to the organic goo-Kerogen, that is a precursor to other forms of hydrocarbon maturation. Flow through the formation is its 'permeability' and that is a property of the rock.

Leave a comment

First Name

Last Name

Email

That email address is already in the database. Please login to your account to post your comment, or enter a different email address to continue with your comment & account creation.

Captcha

Comment

Please understand that, by submitting this form, you will be creating a free OilPrice.com account, and therefore agree to abide by our Terms of Use. Your details will be stored in our database and shared with our third party mailing list provider. You will be sent an email containing a link that will ask you to generate a new password - please follow the link to complete your OilPrice account activation.

We will save the information entered above in our website. Your comment will then await moderation from one of our team. If approved, your data will then be publically viewable on this article. Please confirm you understand and are happy with this and our privacy policy by ticking this box. You can withdraw your consent, or ask us to give you a copy of the information we have stored, at any time by contacting us.